The present invention relates to a quantum thin line producing method for forming a quantum thin line constructed of a metal or semiconductor that is minute enough to cause a quantum size effect on an insulating substrate or a semiconductor substrate via an insulating layer and to a semiconductor device employing this quantum thin line.
The large-scale integrated circuits (LSIs) that have supported the development of electronics and currently become the industrial nucleus have made great strides in terms of their performances toward larger capacity, higher speed, lower consumption of power and so on through the microstructural progress thereof. However, it is considered that the conventional device reaches the limit in terms of the principle of operation when the device size becomes 0.1 xcexcm or smaller, and accordingly, there are conducted energetic researches on a new device based on a new principle of operation. As for this new device, there is a device having a microstructure called the nanometer-size quantum dot or quantum thin line. The nanometer-size quantum dot is energetically examined together with a variety of quantum effect devices, particularly for the application thereof to a single electron device utilizing the Coulomb blockade phenomenon. The nanometer-size quantum thin line is expected to be applied to a super high-speed transistor utilizing the quantum effect.
Particularly, in regard to the nanometer-size quantum thin line, there is carried out trial production of a semiconductor quantum device based on a new principle of operation that the degree of freedom of an electron is limited by confining the electron in a semiconductor layer having a width approximately equal to that of the electron wavelength (de Broglie wavelength) in a semiconductor crystal and a quantization phenomenon caused by this is utilized. That is, the wavelength of an electron in a semiconductor layer is about 10 nm. Therefore, it is theoretically derived that, if an electron is confined in a semiconductor thin line (quantum thin line) having a width of about 10 nm, then the electron can move in this thin line while being scarcely deviated, for the achievement of the increased mobility of the electron.
Therefore, by forming a conductive layer in which a number of quantum thin lines as described above are arranged in a plane and controlling the number of electrons inside this conductive layer by the operation of a gate electrode, there can be produced a quantum thin line transistor having a higher operating speed than the conventional transistor. By incorporating a number of quantum thin lines as described above into a laser light emitting layer, there can be obtained a high-efficiency semiconductor laser device that has a sharp spectrum and excellent high-frequency characteristics even with a small injection current.
Conventionally, as a method for forming the aforementioned quantum thin line, there have been proposed methods as disclosed in the following reference documents (1) through (3).
(1) Ishiguro, et al., Japan Society of Applied Physics, spring in 1996, Lecture No. 28a-PB-5, proceeding p-798 and Lecture No. 26p-ZA-12, proceeding p-64
FIGS. 15A through 15D are process charts showing the xe2x80x9cMethod for uniformly producing Si quantum thin line on a SIMOX (separation by implanted oxygen) substrate utilizing anisotropic etchingxe2x80x9d disclosed in the above reference document (1).
Referring to FIGS. 15A through 15D, first, as shown in FIG. 15A, silicon nitride (Si3N4) is deposited on a (100)-SIMOX substrate constructed of a silicon substrate 1, an oxide film 2 and a SOI (silicon-on insulator) film 3, and thereafter patterning is performed to form a silicon nitride film 4. Next, as shown in FIG. 15B, anisotropic etching is performed with TMAH (tetramethylammonium hydroxide) using the silicon nitride film 4 as a mask, consequently forming a. SOI film 5 having a (111) plane on a pattern edge.
Next, as shown in FIG. 15C, the (111) plane of the side wall of the SOI film 5 is selectively oxidized using the silicon nitride film 4 as a mask, consequently forming an oxide film 6. Then, as shown in FIG. 15D, the silicon nitride film 4 is removed, and thereafter anisotropic etching is performed again with TMAH using the oxide film 6 as a mask, consequently forming a Si quantum thin line 7.
The width of this Si quantum thin line 7 is determined depending on the film thickness of the SOI film 3, and practically a thin line of about 10 nm is formed. In a quantum thin line MOSFET (metal-oxide-semiconductor field-effect transistor) formed by employing the thus-formed Si quantum thin line 7 as a channel region, there is observed Coulomb blockade vibration that is the characteristic of the quantization phenomenon.
(2) Japanese Patent Laid-Open Publication No. HEI 6-77180
FIGS. 16A through 16C are process charts showing the xe2x80x9cquantum thin line forming method utilizing thin-line-shaped etching mask by side wall methodxe2x80x9d disclosed in the above reference document (2).
Referring to FIGS. 16A through 16C, first, as shown in FIG. 16A, a resist 12 is formed by patterning on a substrate 11 of GaAs to be etched, and a SiO2 film 13 having a film thickness of 50 nm is further formed on them by plasma-activated chemical vapor deposition (PCVD). Next, as shown in FIG. 16B, reactive ion etching is performed to form a side wall 14 of SiO2 on both side walls of the patterned resist 12.
Finally, as shown in FIG. 16C, the resist 12 is removed, and thereafter the substrate 11 of GaAs to be etched is patterned by reactive ion etching using the SiO2 side wall 14 as a mask, consequently forming a thin line made of GaAs.
(3) Japanese Patent Laid-Open Publication No. HEI 8-288499
FIGS. 17A through 17G are process charts showing the xe2x80x9cquantum thin line forming method utilizing sticking of two Si wafers and etching mask of wall formationxe2x80x9d disclosed in the above reference document (3).
Referring to FIGS. 17A through 17G, first, as shown in FIG. 17A, a protruding portion 22 is formed on a Si substrate 21 by dry etching. Subsequently, as shown in FIG. 17B, a SiOx-based insulating film 23 is formed so as to flatten the entire substrate. Next, as shown in FIG. 17C, the flattened substrate is entirely inverted and stuck on another Si substrate 24 with the SiOx-based insulating film 23 side put in contact with the substrate 24. Next, as shown in FIG. 17D, the Si substrate 21 is abraded by the CMP (chemical-mechanical polishing) method until the SiOx-based insulating film 23 is exposed. As a result, an island-shaped Si layer 25 of a thickness of about 10 nm is left as buried in the SiOx-based insulating film 23. Then, by forming a polysilicon layer including an impurity to a thickness of about 10 nm by the thermal CVD (chemical vapor deposition) method and thereafter performing anisotropic etching via a resist mask (not shown), there is formed a polysilicon pattern 26 where the processed end surface is positioned in the vicinity of the center of the island-shaped Si layer 25.
Next, as shown in FIG. 17E, a thermo-oxidized film (SiOx) 27 having a film thickness of 1 nm to 10 nm is formed on the Si exposed portions 25 and 26 through a thermo-oxidizing process. Next, as shown in FIG. 17F, by etching back performed, a side wall 28 is formed with the thermo-oxidized film 27 left on the processed end surface of the polysilicon pattern 26. Next, as shown in FIG. 17G, the island-shaped Si layer 25 is subjected to wet processing on condition that a selection ratio relative to the island-shaped layer 25 can be assured, consequently removing the polysilicon pattern 26. Subsequently, the island-shaped Si layer 25 is etched on condition that the selection ratio relative to SiOx that forms the side wall 28 can be assured, consequently forming a quantum thin line 29.
However, the conventional quantum thin line forming methods disclosed in the aforementioned reference documents (1) through (3) have the following problems. That is, the reference (1) is the method effective only when the substrate is made of SOI and is not applicable to the conventionally used Si substrate. The SOI substrate costs ten to twenty times the price of the Si substrate, and it is preferable to form the quantum thin line with the Si substrate in order to further reduce the cost.
Furthermore, according to the aforementioned reference (2), the side wall that determines the width of the quantum thin line is formed by CVD and reactive ion etching. However, there is the problem that the width of the quantum thin line is required to be controlled within a range of 1 nm to 10 nm and it is difficult to control the thickness of the film formed by PCVD and side wall etching within the range of 1 nm to 10 nm.
Furthermore, according to the aforementioned reference (3), there are needed two Si substrates 21 and 24 to be stuck on each other, and there is needed the special substrate forming technique of sticking the two Si substrates 21 and 24 on each other via the insulating film 23. The height of the quantum thin line 29 to be formed is determined depending on the depth when dry etching the Si substrate 21 via the resist mask. In the above case, there is a problem that it is very difficult to control the dry etching depth in nanometer size. There is another problem that the width of the quantum thin line 29 depending on the width of the side wall 28 is hardly controlled.
Accordingly, the object of the present invention is to provide a quantum thin line producing method capable of forming a nanometer-size quantum thin line with a semiconductor substrate of a Si substrate, a GaAs substrate or the like by means of the general film forming technique, lithographic technique and etching technique as well as a semiconductor device employing the quantum thin line.
In order to achieve the aforementioned object, the present invention provides a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second nitride film on the first oxide film and the patterned first nitride film and forming a second oxide film by oxidizing the surface of the second nitride film; a process for forming a third nitride film on the second oxide film; a process for masking a portion that belongs to the third nitride film and extends from a center portion to a lower portion of a stepped portion based on an end portion of the first nitride film and etching back an upper portion of the stepped portion, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing by dry etching the second oxide film that extends in a direction perpendicular to an upper surface of the semiconductor substrate and is put between the second nitride film and the third nitride film using the second nitride film and the third nitride film as a mask, consequently forming a groove; a process for removing by etching the second nitride film located under the groove and the first oxide film located under the second nitride film, consequently exposing the semiconductor substrate; a process for removing the first nitride film together with the second nitride film and the third nitride film facing the groove; a process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film, the second nitride film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the groove for exposing the semiconductor substrate that becomes the portion where the quantum thin line is epitaxially grown is formed by the general film forming technique, lithographic technique and etching technique. Therefore, the positional control of the quantum thin line can be enabled. The width of the groove for determining the width of the quantum thin line is determined depending on the film thickness of the second oxide film formed by oxidizing the surface of the second nitride film. Therefore, the width of the quantum thin line is accurately controlled. Furthermore, the quantum thin line is formed through epitaxial growth, and therefore, a quantum thin line having excellent crystallinity and good uniformity of size and density is formed with good reproducibility. Since the quantum thin line is made to epitaxially grow on the exposed portion of the semiconductor substrate, the quantum thin line can be formed by using the semiconductor substrate of the Si substrate that has conventionally been used. In the above case, the width of the groove where the quantum thin line grows is determined depending on the film thickness of the second oxide film formed by oxidizing the surface of the second nitride film. Therefore, the width can be controlled in nanometer size, and accordingly the width of the quantum thin line can be set in nanometer size. Furthermore, after the growth of the quantum thin line, oxidation is performed to isolate the quantum thin line from the semiconductor substrate by the third oxide film. Therefore, the bottom surface side of the quantum thin line is not put in contact with the semiconductor substrate, allowing the electron to be completely confined. Since one semiconductor substrate is used, there is not needed the special substrate forming technique of sticking two Si substrates on each other via the insulating layer, and the quantum thin line can be easily formed at low cost.
As described above, there is provided a quantum thin line producing method of a high yield and high productivity appropriate for mass production at reduced producing cost without using any special fine processing technique.
According to the present invention, there is provided a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second nitride film on the first oxide film and the patterned first nitride film and forming a second oxide film by oxidizing the surface of the second nitride film; a process for forming a third nitride film on the second oxide film; a process for masking a portion that belongs to the third nitride film and extends from a center portion to a lower portion of a stepped portion based on an end portion of the first nitride film and etching back an upper portion of the stepped portion, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for forming a fourth nitride film; a process for etching back the fourth nitride film, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing by dry etching the second oxide film that extends in a direction perpendicular to an upper surface of the semiconductor substrate and is put between the second nitride film and the third nitride film using the second nitride film, the third nitride film and the fourth nitride film as a mask, consequently forming a groove; a process for removing by etching the second nitride film located under the groove and the first oxide film located under the second nitride film, consequently exposing the semiconductor substrate; a process for removing the first nitride film together with the second nitride film, the third nitride film and the fourth nitride film facing the groove; a process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film, the second nitride film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the third nitride film is etched back to expose the second oxide film on the first nitride film, and thereafter the fourth nitride film is formed. With this arrangement, even if the second oxide film located between the first nitride film patterns and the mask is disadvantageously exposed due to the wide interval between the edge of the mask for etching back use and the edge of the first nitride film when etching back the third nitride film, then the portion is covered with the fourth nitride film. Thus, the positional control margin of the end surface of the mask is about doubled, and this improves the workability and accuracy of the positional control.
According to the present invention, there is provided a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second nitride film on the first oxide film and the patterned first nitride film and forming a second oxide film by oxidizing the surface of the second nitride film; a process for forming a third nitride film on the second oxide film; a process for masking a portion that belongs to the third nitride film and extends from a center portion to a lower portion of a stepped portion based on an end portion of the first nitride film and etching back an upper portion of the stepped portion, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for forming a fourth nitride film; a process for etching back the fourth nitride film, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing the second oxide film and the second nitride film located above the first nitride film; a process for reducing by etching back the first nitride film, the third nitride film and the fourth nitride film in film thickness and lowering in height the second nitride film that extends in the direction perpendicular to an upper surface of the semiconductor substrate; a process for removing by dry etching the second oxide film that extends in a direction perpendicular to the upper surface of the semiconductor substrate and is put between the second nitride film and the third nitride film using the second nitride film, the third nitride film and the fourth nitride film as a mask, consequently forming a groove; a process for removing by etching the second nitride film located under the groove and the first oxide film located under the second nitride film, consequently exposing the semiconductor substrate; a process for removing the first nitride film together with the second nitride film, the third nitride film and the fourth nitride film facing the groove; a process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film, the second nitride film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the fourth nitride film is etched back to expose and remove the second oxide film on the first nitride film, and thereafter the first, third and fourth nitride films are etched back, as a consequence of which only the second oxide film extending in the perpendicular direction protrudes from the surface. The aspect ratio of etching relative to the perpendicular second oxide film is thus reduced, allowing the groove for exposing the semiconductor substrate to be easily formed.
According to the present invention, there is provided a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second oxide film on the first oxide film and the patterned first nitride film; a process for forming a second nitride film on the second oxide film; a process for masking a portion that belongs to the second nitride film and extends from a center portion to a lower portion of a stepped portion based on an end portion of the first nitride film and etching back an upper portion of the stepped portion, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing by dry etching the second oxide film that extends in a direction perpendicular to an upper surface of the semiconductor substrate and is put between the first nitride film and the second nitride film together with the first oxide film located under the second oxide film using the first nitride film and the second nitride film as a mask, consequently forming a groove for exposing the semiconductor substrate; process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the groove obtained by exposing the semiconductor substrate is formed by the general film forming technique, lithographic technique and etching technique. Therefore, the positional control of the quantum thin line is enabled. Furthermore, the width of the groove for determining the width of the quantum thin line is set by the film thickness of the second oxide film, and therefore, the width of the quantum thin line is accurately controlled. The quantum thin line is formed through epitaxial growth, a quantum thin line having excellent crystallinity and good uniformity of size and density is formed with good reproducibility. Furthermore, the second oxide film is formed without oxidizing the nitride film, and therefore, the processes are reduced for simplification by the nitride film forming process for forming the second oxide film.
According to the present invention, there is provided a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second oxide film on the first oxide film and the patterned first nitride film; a process for forming a second nitride film on the second oxide film; a process for masking a portion that belongs to the second nitride film and extends from a center portion to a lower portion of a stepped portion based on an end portion of the first nitride film and etching back an upper portion of the stepped portion, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for forming. a third nitride film; a process for etching back the third nitride film, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing by dry etching the second oxide film that extends in a direction perpendicular to an upper surface of the semiconductor substrate and is put between the first nitride film and the second nitride film together with the first oxide film located under the second oxide film using the first nitride film, the second nitride film and the third nitride film as a mask, consequently forming a groove for exposing the semiconductor substrate; a process for removing the first nitride film, the second nitride film and the third nitride film; a process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the second nitride film is etched back to expose the second oxide film on the first nitride film, and thereafter the third nitride film is formed. With this arrangement, even if the second oxide film located between the first nitride film patterns and the mask is disadvantageously exposed due to the wide interval between the edge of the mask for etching back use and the edge of the first nitride film when etching back the second nitride film, then the portion is covered with the third nitride film. Thus, the positional control margin of the end surface of the mask is about doubled, and this improves the workability and -accuracy of the positional control.
According to the present invention, there is provided a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second oxide film on the first oxide film and the patterned first nitride film; a process for forming a second nitride film on the second oxide film; a process for masking -a portion that belongs to the second nitride film and extends from a center portion to a lower portion of a stepped portion based on an end portion of the first nitride film and etching back an upper portion of the stepped portion, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for forming a third nitride film; a process for etching back the third nitride film, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing the second oxide film located above the first nitride film; a process for reducing the first nitride film, the second nitride film and the third nitride film in film thickness; a process for removing by dry etching the second oxide film that extends in a direction perpendicular to an upper surface of the semiconductor substrate and is put between the first nitride film and the second nitride film together with the first oxide film located under the second oxide film using the first nitride film, the second nitride film and the third nitride film as a mask, consequently forming a groove for exposing the semiconductor substrate; a process for removing the first nitride film, the second nitride film and the third nitride film; a process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the third nitride film is etched back to expose and remove the second oxide film on the first nitride film, and thereafter the first, second and third nitride films are etched back, as a consequence of which only the second oxide film extending in the perpendicular direction protrudes from the surface. The aspect ratio of etching relative to the perpendicular second oxide film is thus reduced, allowing the groove for exposing the semiconductor substrate to be easily formed.
According to the present invention, there is provided a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second nitride film on the first oxide film and the patterned first nitride film and forming a second oxide film by oxidizing the surface of the second nitride film; a process for forming a third nitride film on the second oxide film, consequently burying a recess portion located between portions of the first nitride film; a process for etching back the third nitride film, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing by etching the second oxide film that extends in a direction perpendicular to an upper surface of the semiconductor substrate and is put between the second nitride film and the third nitride film using the second nitride film and the third nitride film as a mask, consequently forming a groove; a process for removing by etching the second nitride film located under the groove and the first oxide film located under the second nitride film, consequently exposing the semiconductor substrate; a process for removing the first nitride film together with the second nitride film and the third nitride film facing the groove; a process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film, the second nitride film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the space between the adjacent first nitride film patterns is buried under the third nitride film, and this third nitride film is etched back to expose the second oxide film on the -first nitride film. In this case, if the interval between the adjacent first nitride film portions is narrow to a certain extent, then the third nitride film is left between both the first nitride film portions. Therefore, the mask for etching back the third nitride film is not needed, and this simplifies the processes and reduces the producing cost.
According to the present invention, there is provided a quantum thin line producing method comprising: a process for forming a first oxide film on a semiconductor substrate and forming a patterned first nitride film on the first oxide film; a process for forming a second oxide film on the first oxide film and the patterned first nitride film; a process for forming a second nitride film on the second oxide film, consequently burying a recess portion located between portions of the first nitride film; a process for etching back the second nitride film, consequently exposing a portion that belongs to the second oxide film and is located above the first nitride film; a process for removing by etching the second oxide film that extends in a direction perpendicular to an upper surface of the semiconductor substrate and is put between the first nitride film and the second nitride film together with the first oxide film located tinder the second oxide film using the first nitride film and the second nitride film as a mask, consequently forming a groove for exposing the semiconductor substrate; a process for removing first nitride film and the second nitride film; a process for epitaxially growing a quantum thin line on the exposed portion of the semiconductor substrate; a process for removing the first oxide film and the second oxide film; and a process for forming a third oxide film by oxidizing a lower portion of the quantum thin line, consequently isolating the quantum thin line from the semiconductor substrate by the third oxide film.
According to the above construction, the space between the adjacent first nitride film patterns is buried under the second nitride film, and this second nitride film is etched back to expose the second oxide film on the first nitride film. In this case, if the interval between the adjacent first nitride film portions is narrow to a certain extent, then the second nitride film is left between both the first nitride film portions. Therefore, the mask for etching back the second nitride film is not needed, and this simplifies the processes and reduces the producing cost. Furthermore, the second oxide film is formed without oxidizing the nitride film, and therefore, the processes are reduced for simplification by the nitride film forming process for forming the second oxide film.
In one embodiment, there is provided a quantum thin line producing method, wherein the process for epitaxially growing the quantum thin line comprises the steps of: introducing the semiconductor substrate on which the groove for exposing the semiconductor is formed into a reaction chamber and discharging air inside the reaction chamber so that the reaction chamber comes to have a high vacuum of not higher than 10xe2x88x926 Torr; and thereafter flowing a material gas into the reaction chamber so as to perform vapor growth of the quantum thin line under a material gas partial pressure of not higher than 10xe2x88x922 Torr.
According to the above embodiment, the atmospheric components and the impurities of moisture component and the like are discharged so that the reaction chamber comes to have a high vacuum of not higher than 10xe2x88x926 Torr, consequently promoting the epitaxial growth in the highly clean environment. Then, during the epitaxial growth, the material gas partial pressure is controlled under a pressure of not higher than 10xe2x88x922 Torr, and this prevents the rapid start of film growth on the entire surface of the insulating thin film and allows the selective vapor growth of the quantum thin line only in the groove obtained by exposing the semiconductor substrate. Thus, the degree of vacuum inside the reaction chamber, the amount of material gas to be introduced, the time of introduction, the substrate temperature and so on are controlled by means of a general high-vacuum CVD apparatus, by which the quantum thin line of the desired size is formed with high reproducibility.
In one embodiment, a silicon thin line is formed as the quantum thin line using any one of monosilane (SiH4), disilane (Si2H6), trisilane (Si3H.), dichlorosilane (SiH2Cl2) and tetrachlorosilane (SiCl4) as a material gas.
According to the above embodiment, a quantum thin line made of silicon is formed by using any one of SiH4, Si2H6, Si3H8, SiH2Cl2 and Si4 as the reaction gas, by which the uniformity of size and the reproducibility of the quantum thin line are further improved.
In one embodiment, a germanium thin line is formed as the quantum thin line using any one of monogermane (GeH4), digermane (Ge2H6) and germanium tetrafluoride (GeF4) as a material gas.
According to the above embodiment, a quantum thin line made of germanium is formed by using any one of GeH4, Ge2H6 and GeF4 as the reaction gas, by which the uniformity of size and the reproducibility of the quantum thin line are further improved.
In one embodiment, a silicon germanium thin line is formed as the quantum thin line using a mixed gas comprised of any one of monosilane (SiH4), disilane (Si2H6), trisilane (Si3H8), dichlorosilane (SiH2Cl2) and tetrachlorosilane (SiCl4) and any one of monogermane (GeF4), digermane (Ge2H6) and germanium tetrafluoride (GeF4) as a material gas.
According to the above embodiment, a quantum thin line made of silicon germanium is formed by using a mixed gas of any one of SiH4, Si2H6, Si3H8, SiH2Cl2 and SiCl4 and any one of GeH4, Ge2H6 and GeF4 as the reaction gas, by which the uniformity of size and the reproducibility of the quantum thin line are further improved.
In one embodiment, an aluminum thin line is formed as the quantum thin line using an organic aluminum.
According to the above embodiment, a quantum thin line made of aluminum is formed by using an organic aluminum of dimethyl aluminum hydride (DMAH: (CH3)2AlH) or the like as a material, by which the uniformity of size and the reproducibility of the quantum thin line are further improved.
According to the present invention, there is provided a semiconductor device having a source region, a drain region, a channel region located between the source region and the drain region, a gate region for controlling a channel current flowing through the channel region, a floating gate region located between the gate region and the channel region, a first insulating film located between the floating gate region and the gate region and a second insulating film located between the channel region and the floating gate region, the floating gate region being comprised of a quantum thin line formed by the quantum thin line producing method.
According to the above construction, the quantum thin line is used as the floating gate region of the transistor, by which the electric charge accumulation is reduced and the amount of electric charges to be injected Iinto the floating gate region is reduced. This enables the obtainment of a non-volatile memory of a small consumption of power, a high density and a large capacity. Furthermore, the quantum thin line can be formed by the general film forming technique, lithographic technique and etching technique. Therefore, a non-volatile memory of a high yield and high productivity appropriate for mass production can be obtained at low cost. Furthermore, the non-volatile memory having the quantum thin line that becomes the basis of the single electron device can be mounted on the same substrate as that of a Si-based LSI.
According to the present invention, there is provided a semiconductor device having a source region, a drain region, a channel region located between the source region and the drain region, a gate region for controlling a channel current flowing through the channel region and a gate insulating film located between the channel region and the gate region, the channel region being comprised of a quantum thin line formed by the above quantum thin line producing method.
According to the above construction, the channel region of the transistor is constructed of the quantum thin line, by which the channel region is quantized in the id direction perpendicular to the lengthwise direction, exhibiting linear conduction. As a result, a super-high speed operation is enabled, allowing a transistor of a high yield and high productivity appropriate for mass production to be obtained at low cost. Furthermore, the transistor having the quantum thin line that becomes the basis of the single electron device can be mounted on the same substrate as that of a Si-based LSI.
According to the present invention, there is provided a semiconductor device comprising: a quantum thin line formed by the above quantum thin line producing method; a first insulating film and a second insulating film laminated with interposition of the quantum thin line; a first electrode formed on the first insulating film; and a second electrode formed on the second insulating film, whereby the quantum thin line emits light when a voltage is applied across the first electrode and the second electrode.
According to the above construction, by virtue of the quantum confining effect produced by putting the quantum thin line between the insulating film portions and further between the electrodes, the quantum thin line has a direct transition type band structure. Therefore, by making a tunnel current flow with a voltage applied across both the electrodes so as to inject electrons into the quantum thin line, electron transition occurs in the quantum thin line, causing light emission. Thus, a high-efficiency light-emitting-device of excellent high-frequency characteristics having a sharp spectrum even with a small injection current can be obtained at low cost with a high yield and high productivity. Furthermore, the semiconductor device having the quantum thin line that becomes the basis of the quantum effect device or the single electron device can be mounted on the same substrate as that of the Si-based LSI. By applying this semiconductor device to a light-emitting device or a photoelectric transducing device, an electronic circuit and an optical communication circuit can be combined with each other.
According to the present invention, there is provided a semiconductor device comprising: a quantum thin line formed by the above quantum thin line producing method; an n-type impurity region formed in a portion of the quantum thin line; and a p-type impurity region formed in contact with the n-type impurity region on the quantum thin line, whereby a junction region of both the impurity regions of the quantum thin line emits light when a voltage is applied across the n-type impurity region and the p-type impurity region.
According to the above construction, a pn junction is formed of the n-type impurity region and the p-type impurity region in the quantum thin line, where the direct transition type band structure is provided by the quantum confining effect. Therefore, by applying a voltage to the n-type impurity region and the p-type impurity region, reunion of an electron with a hole occurs in the pn junction portion, consequently emitting light. Thus, a high-efficiency light-emitting device of excellent high-frequency characteristics having a sharp spectrum even with a small injection current can be obtained at low cost with a high yield and high productivity. Furthermore, the semiconductor device having the quantum thin line that becomes the basis of the quantum effect device or the single electron device can be mounted on the same substrate as that of the Si-based LSI. By applying this semiconductor device to a light-emitting device or a photoelectric transducing device, an electronic circuit and an optical communication circuit can be combined with each other.
According to the present invention, there is provided a semiconductor device having a quantum thin line formed by the above quantum thin line producing method, wherein a forbidden bandwidth of a first region of the quantum thin line is made smaller than a forbidden bandwidth of two second regions positioned on both sides of the first region, and the first region emits light when a voltage is applied across both the second regions.
According to the above construction, the quantum thin line has the direct transition type band structure by the quantum confining effect. Due to the fact that the forbidden bandwidth of the first region located in the center portion is smaller than the forbidden bandwidth of the second regions located on both sides, a double hetero structure in which the efficiency of reunion of an electron with a hole is high is provided. Therefore, by applying a voltage to the two second regions located on both sides of the first region, the reunion of an electron with a hole occurs in the second region, consequently emitting light. Thus, a high-efficiency light-emitting device or an optical transducing device of excellent high-frequency characteristics having a sharp spectrum even with a small injection current can be obtained at low cost with a high yield and high productivity. Furthermore, the semiconductor device having the quantum thin line that becomes the basis of the quantum effect device or the single electron device can be mounted on the same substrate as that of the Si-based LSI. By applying this semiconductor device to a light-emitting device or a photoelectric transducing device, an electronic circuit and an optical communication circuit can be combined with each other.